1870. ] IN THE GROWTH OF SALMON. 39 
Dr. Giinther himself professes to have been sceptical concerning 
hybrid Salmonoids under natural conditions, until convinced, through 
the Rev. Augustus Morgan, of a cross between the Sewin (S. cambri- 
cus) and the River-trout (S. fario)*. 
It is said “These hybrids are so numerous in the Rhymney and 
other rivers of South Wales, and so variable in their characters, that 
the passage from one species to the other may be demonstrated in 
an almost unbroken series, which might induce some naturalists to 
regard both species as identical.” They retain the migratory impulse 
seawards, and are sexually developed in the autumn,—when young, 
are like Trout—when older, Sewin. On their first ascent from the 
sea they are slightly smaller, but closely resemble Sewin. On their 
second migratory return they are darker and redder than either 
supposed parent. These equivocal hybrids, W. Peel, Esq., of 
Taliaris Park, retained for years in a freshwater pond, where they 
grew from 15 to 18 inches long, but remained sterile. Males pre- 
ponderate. 
It is not stated precisely on what evidence these fishes claim hybri- 
dity, more than that they bear resemblances to both species. Indeed, 
from Dr. Giinther’s own descriptions, the Sewin characters prepon- 
derate. If, therefore, Siebold’s observations, checked by Widegren’s 
subsequent data (viz. that some individuals of every Salmonoid 
species are very late in being sexually developed, or have as it werea 
longer temporary immaturity, and during such period differ from 
those normally developed), be applied to this instance of hybridism, 
it may on such grounds be maintained that the said hybrids are 
after all nothing but retarded examples of S. cambricus. 
Taken in this light, these so-called hybrids offer coincident ana- 
logies to the retarded conditions assumed to occur in S. salar, and 
notably in those two specimens which have formed the basis of the- 
present paper. 
It seems to me also a legitimate inference that the two fishes reared 
in our aquarium are Salmon, inasmuch as they differ in a far greater 
degree from all other European species than from S.salar. Indeed, 
as 1s broadly admitted in the British-Museum Catalogue, p. 3, of the 
genus Salmo, “The almost infinite variations of these fishes are 
dependent on age, sex and sexual development, food, and the pro- 
perties of the water ;” hence this very same reasoning which de- 
monstrates peculiarities in the two Salmonoids and brood in question, 
logically points to their immaturity, retardation, or masking of the 
normal adult characters of the species. If their entire growth has 
been prejudicially influenced by continuous retention in fresh water, 
so may a defect or abnormal number of scales (two transversely) and 
pyloric appendages (three or four) be but the concomitant effect of 
unnatural development. 
Suppose, again, our oft-quoted Garden specimens were a cross 
breed between any two well-known species, freshwater or marine, 
there remains still a wide loophole of doubt why they have remained 
so very small-sized. No European species whatever, to my know- 
* See B. M. Cat. of Fishes, vol. vi: p. 8. 
